Barack Obama swore for a second time to “protect and defend” the US constitution at a private White House ceremony, an oath he will repeat for hundreds of thousands of people today.

The day of festivities, parades and fancy dress balls will mark the beginning of Mr Obama’s second four-year term as America’s first black president.

In a speech to hundreds of supporters at Washington DC’s National Building Museum in the early hours of today, Mr Obama said his second inauguration was a celebration of the country and its citizens, not the election results.

“What we’re doing is celebrating each other and celebrating this incredible nation that we call home,” he said.

He encouraged the crowd to enjoy the inauguration and said he needed them to work as hard as they could on issues important to them.

Mr Obama said the inauguration was a reminder that “there is something bigger than ourselves”. He kept his comments brief, quipping that he had to save some of his lines for his speech later.

First lady Michelle Obama, holds the Robinson Family Bible as her husband Barack is officially sworn-in for his second term as US president

The politician who rose improbably from a history as a community organiser in Chicago and a professor of constitutional law to the pinnacle of power faces a nation riven by partisan disunity, a still-weak economy and an array of challenges abroad.

Mr Obama will take the oath again before the crowd on the steps of the US Capitol and is expected to follow the recent tradition of walking at least part of the way back to the White House, surrounded by cheers.

In the briefest of ceremonies yesterday, with his family gathered in the White House, Mr Obama took the oath of office shortly before noon, as required by law. With his left hand on a family bible held by first lady Michelle Obama, the 44th president raised his right hand and repeated the time-honoured words read out by Supreme Court Chief Justice John Roberts.

The intimate swearing-in met the legal requirement that presidents officially take office on January 20. Because that date fell on a Sunday this year, the traditional public ceremonies surrounding the start of a president’s term were put off to today, which coincides this year with the birthday of revered civil rights leader Martin Luther King.

Mr Obama made no special remarks at Sunday’s ceremony. “I did it,” he said quietly to his youngest daughter Sasha, before wrapping her in a hug. The oath went smoothly, unlike four years ago, when Chief Justice Roberts made mistakes while trying to recite the oath from memory and had to do it again with Mr Obama later.

Today’s events are expected to have less of the effervescence of four years ago, when the 1.8 million people packed into central Washington knew they were witnessing history.

Mr Obama is now older, greyer and more entrenched in the politics he once tried rise above. Officials are expecting 500,000 to 700,000 people to turn out.